Field of the Invention
The present invention relates to a biometric recognition apparatus, especially to biometric recognition apparatus for fingerprint recognition.
Description of Prior Art
Biometric recognition technologies have rapid development due to the strong request from electronic security applications and automatic access control system. The biometric recognition technologies can be classified into fingerprint recognition, iris recognition and DNA recognition and so on. For the considerations of efficiency, safety and non-invasiveness, the fingerprint recognition becomes main stream technology. The fingerprint recognition device can scan fingerprint image by optical scanning, thermal imaging or capacitive imaging. For cost, power-saving, reliability and security concerns, the capacitive fingerprint sensor becomes popular for biometric recognition technology applied to portable electronic devices.
The conventional capacitive fingerprint sensors can be classified into swipe type and area type (pressing type), and the area type has better identification correctness, efficiency and convenience. However, the area type capacitive fingerprint sensor generally integrates the sensing electrodes and the sensing circuit into one integrated circuit (IC) protected by a sapphire film with thickness below 100 um because the sensed signals are minute and the background noise is huge in comparison with the minute sensed signals. As a result, the material cost and package cost is high while the product lifetime and durability are influenced. It is a development trend to enhance the sensing ability and signal-to-noise ratio for the sensing circuit such that the sensing electrodes can be placed on the substrate other than that for integrated circuit (IC). Therefore, the sensing area can be increased while the cost can be decreased. Moreover, the lifetime and durability are enhanced.
The conventional finger-swiping recognition apparatus have following schemes. The sensing electrodes and the sensing circuit are integrated in a single IC. Alternatively, mutual electrodes for capacitance are formed on thin films and packaged in chip on film (COF) architecture to provide mutual capacitance sensor. The former finger-swiping recognition apparatus has higher cost and poor durability. The later finger-swiping recognition apparatus has poor recognition accuracy. It is desirable to provide a biometric recognition apparatus to have low cost and accurate recognition as well as long lifetime.
It is an object of the invention to overcome above-mentioned problems.
In one aspect of the present invention, the biometric recognition apparatus has at least one row of sensing electrodes and has shielding electrode and uses self-capacitance sensing scheme, thus reducing cost and enhancing the recognition accuracy and product lifetime.